This invention relates to vehicle height adjusting devices of the kind including a source of pressurized air and an elevating device receiving pressurized air from the source in elevating the height of a vehicle and exhausting pressurized air therefrom in descending the height of the vehicle.
Conventionally, the source of pressurized air comprises an air compressor and an air tank storing pressurized air supplied from the air compressor. The air compressor is operated when the pressure in the air tank decreases below a predetermined level, and the operation of the air compressor is terminated when a pressure in the air tank exceeds a second predetermined level which is higher than the first mentioned level. The operation of the air compressor has been performed independently of the height of the vehicle. Further, a height detector is provided to control the supply or exhaust of pressurized air into or from the elevating device, and a dehumidifying device is provided between the air compressor and the air tank to remove water from the pressurized air produced in the air compressor, and for regenerating or reactivating the dehumidifying device the pressurized air exhausted from the elevated device is passed through the dehumidifying device in the direction opposite to that of the pressurized air produced in the air compressor. Thus, there is a problem such that when the pressure in the air tank is lower than a predetermined level and the height of the vehicle is higher than a predetermined level, the pressurized air produced in the air compressor tends to flow through the dehumidifying device in one direction and pressurized air exhausted from the elevating device tends to flow through the dehumidifying device in the opposite direction. The operation of the air compressor is not satisfactorily performed and, also, the pressurized gas in the elevating device is not satisfactorily exhausted. As a result, the supplying and exhausting operations are excessively prolonged and, finally, either one operation is terminated satisfying the object thereof and, thereafter, the other operation is terminated. Therefore, the height of the vehicle cannot smoothly be adjusted and, there are considerable amounts of losses of the energy and of the movement of related members. Further, the device may become out of order.
Such phenomenon will be observed in conventional vehicle height adjusting devices when passengers get out of the vehicle or a cargo is discharged in operating the air compressor.